It has been proposed to produce a core for a heat exchanger, such as a radiator for an automobile by making an assembly which comprises thin tubes and fin elements in an alternate relationship. The cooling tubes are usually made of copper or brass. The fin elements are then usually manufactured of tapes of copper or brass. During the manufacture of the assembly the tubes and the fin elements are tinned and are then joined together by soldering.
When carrying out the soldering operation it is usual to advance the alternate tube and fin elements along a transportation path through a heating device which provides a sufficient high temperature to melt a tin coating formed on the elements during a preparatory tinning step, so that the abutting elements are joined by soldering when the temperature is reduced after the passage of the elements through the heating device. In order to obtain strong soldered connections, it is necessary that the tubes and the fin elements abut against each other with a firm constant pressure. Devices for providing such a constant pressure, such as devices which provide a pressure opposing the advancing of the elements have been suggested. International patent application No. PCT/SE79/00153, published under International Publication No. WO 80/00228 on Feb. 21, 1980 discloses an apparatus for assembling a heat exchanger core in which an assembly of fin elements and tubes, which are pre-tinned, are passed sequentially through a heating zone and a cooling zone. The assembly is driven forwardly into the heating and cooling zones by two co-operating conveyor belts, and two further co-operating conveyor belts at the point of discharge from the cooling zone act to provide a force in the reverse direction so that the elements are abutted firmly together. Thus the described apparatus is complex.
British patent specification No. 1,449,296 relates to an apparatus for assembling a heat exchanger in which tubes and fin elements are assembled to form a stack, and the stack is advanced with stepped synchronism with successive deliveries of tubes or fin elements at an assembly station. Co-operating pinch rollers act to provide a force to make the elements abut together during a soldering process, but since the stack advances in stepped synchronism, the operation of the pinch rollers is complex.
British patent specification No. 1,525,761 discloses a similar method of assembling a heat exchanger core, but in this method the ends of the tubes forming part of an assembly of tubes and fin elements are linked together before the soldering step to urge the components of the assembly together. The specification also describes an alternative method the ends of the tubes are meshed with advancing chains that perform the same function. This complex devices are provided for maintaining the elements of the assembly in firm contact with each other during the soldering process.
U.S. Pat. No. 3,431,620, describes a further apparatus for assembling tubes and fin elements to form a heat exchanger core in which the tubes and fin elements are automatically assembled in a stack. The stack is then removed by a clamping gauge, and the usual tanks are connected to the elements to form a radiator. There is no disclosure that the elements are soldered or otherwise connected directly together.
It is to be appreciated that where the elements of a heat exchanger are to be advanced through a heating device to solder the elements together the elements should be advanced with an even speed and without shocks. If a shock occurs at the moment, when the molten tin in a prospective soldered seam is going to solidify, the shock can give rise to a substantial deterioration of the soldered seam. When the tubes and the fin elements are arranged in an alternate relationship to form a stack in an assembling device and are advanced to a transportation path by means of an expelling device positioned in or adjacent the assembling device and designed to drive the elements against an existing counterpressure, it is very difficult to avoid shocks in the row of abutting elements.
It is to be understood that with regard to both the manufacturing costs and the quality of the finished product it is desirable to use a continuous soldering procedure of the type described above, provided that the pressure between the adjacent elements that are to be soldered can be kept constant, and shocks and an uneven speed in the transportation path can be avoided.